Thiocarboxylate silanes are extensively used in rubber applications, especially for tires. WO 2005/007660 describes a process in which thiocarboxylate silane is prepared from a corresponding alkanoyl chloride and a chloroalkyltrialkoxy silane using trialkylamines to scavenge the hydrochloric acid by-product. The process requires the use of a stoichiometric amount of amine that is recycled after treatment with caustic to the corresponding hydrochloride. The process is relatively complex and uneconomical.
WO 2005/007661 describes a process for the preparation of thiocarboxylate silane in an aqueous process in the presence of a phase transfer catalyst such as a quaternary ammonium salt or a phosphonium salt. The rate of reaction in this process is low requiring large amounts of catalyst and, as a result, complicated purification procedures.
The manufacture of blocked mercaptosilane from an acyl halide is known from U.S. Pat. No. 6,777,569, but results in a less pure product and a lower yield.